During the tenure of this grant studies on the mechanism of action of a number of enzymes involved in procaryotic DNA replication will be continued. Particular emphasis will be placed on the mechanism of action of the DNA elongation enzymes involving E. coli DNA polymerase III, DNA elongation factors I, III and dna Z. Studies on the specificity of the action of dna G in the synthesis of oligonucleotide primers will be continued. We also plan to examine the mechanism of action of the phi X A protein and the control of phi X RFI replication. The replication of adenoviral DNA will be studied in vitro. The mechanism of initiation and DNA elongation will be examined. Studies will also be carried out on Vaccinia viral transcription and the role of auxiliary proteins on transcription. Included in these studies will be an analysis of reactions ocurring at ends of RNA chains. The latter projects will also be carried out with nuclear extracts of HeLa cells.